PULSATILE RELEASE AND CIRCADIAN-RHYTHMS OF THYROTROPIN AND PROLACTIN IN CHILDREN WITH GROWTH-HORMONE DEFICIENCY

We have measured mean concentrations arid have appraised the pulsatile nature of thyrotropin (TSH) and prolactin (PRL) release in children w ith classical GH deficiency (GHD; n = 4) and neurosecretory GH dysfunc tion (NSD; n = 4) and have compared the results with those obtained in children with constitutional delay (control; n = 4). Blood samples we re obtained at 20-min intervals for 24 h, Pulse analysis of TSH and PR L was undertaken using the Cluster pulse detection algorithm, Circadia n rhythmicity of TSH and PRL was assessed using cosinor analysis, The mean 24-h concentration of GH in the control subjects was significantl y higher than that obtained in the GHD and NSD groups, With regard to TSH, the mean serum concentration in the CHD and NSD group were higher than that of the control subjects. This augmentation reflects TSH pul ses of large amplitude and area, and a higher interpulse valley mean r ather than a difference in peak number or peak duration. No difference s in mean PRL concentration or characteristics of PRL pulses were foun d between the control and GHD and NSD subjects. When the 24 h data set s were divided into day (0800-2000 h) and night (2000-0800 h), the mea n nighttime TSH concentration was higher than the daytime concentratio n ill the control, GHD, and NSD groups. Although there were no day ver sus night differences in TSH pulse frequency in either group, peak amp litude, area, and interpulse valley means were increased during the ni ght in the control group, and peak area, duration, and amplitude mean in the NSD group, The nighttime mean PRL concentrations in the control , GHD, and NSD subjects were higher than those found during the day, T his increase was accounted for by increases in PRL peak amplitude, are a in the control group, and peak area, amplitude, and interpulse valle y mean in the GHD and NSD groups. Cosinor analysis of the 24-h TSH and PRL data revealed clear circadian rhythmicity in all groups of subjec ts. These data suggest that GHD and NSD are associated with an increas e in pulsatile TSH secretion due to an increase in pulse amplitude and interpulse valley mean.